X-ray film is used to capture the image of internal structures of the body through which x-rays are passed. An x-ray cassette is a lightweight housing containing a sheet of x-ray film. An x-ray grid is a grating consisting essentially of a series of narrow lead strips closely spaced on their edges and separated by spacers of low density material. The x-ray grid is used to reduce the amount of scattered radiation reaching the x-ray film. An x-ray grid-cassette is a housing containing both x-ray grid and film. Hereinafter, an x-ray grid-cassette will be referred to as a grid, and an x-ray cassette will be referred to as a cassette.
Surgical procedures often require the taking of x-rays before, during and after the surgery. It is necessary to have flexibility in positioning x-ray grids and cassettes relative to the patient lying on an operating table. It is also necessary for the environment of the operating room to be and remain sterile. During some operations, such as those on the lower back, e.g. lumbar laminectomy, precise x-ray images are critical and require long x-ray exposure times.
Several x-ray cassette holders are available which attach to the operating table and allow an x-ray cassette to be positioned relative to a patient lying on an operating table. For instance, U.S. Pat. No. 2,651,725 issued to A. M. McFarland discloses an x-ray cassette holder which allows a wide range of adjustments of the x-ray cassette relative to the patient.
It is currently common practice in hospitals to sterilize devices in autoclaves. One of the major disadvantages of the prior art cassette holders is that they cannot be sterilized in an autoclave. The size of a typical autoclave oven found in a hospital surgical suite has an opening of 15 inches by 15 inches, and a depth of 27 inches. The size of the prior art x-ray cassette holders, for instance that of McFarland mentioned above, do not enable them to fit within the cavity of the typical autoclave currently found in surgical suites at hospitals, even if they could be autoclaved.
Another disadvantage of the prior art x-ray cassette holders is their capacity to hold only a single x-ray cassette. Certain surgical operations, such as lumbar laminectomy and cervical fusion, require precise x-ray imaging. For such imaging, long exposure times are necessary. During the long exposure time required for lumbar laminectomy, not all the radiation will be absorbed by a single x-ray grid. Some radiation will leak through the single x-ray grid resulting in back scatter radiation and exposing the patient to additional unnecessary radiation. Back scatter radiation obscures the x-ray photograph decreasing the accuracy of the image.